The Udall Center for Excellence in Parkinson Disease Research at the Mayo Clinic is an integrated, multidisciplinary research program of neurologists, neuropsychologists, geneticists, neuropathologists and basic scientists in the study of the "Genetics and Molecular Biology of Parkinsonism." The Center draws upon the clinical strengths of the Mayo Clinic Movement Disorder Section and longitudinal studies of Parkinson disease (PD) and dementia with Lewy bodies (DLB) for the clinical material used in the research projects, as well as strong institutional commitment to PD research. The research proposed is highly synergistic despite the wide range of expertise and scientific background of the members of the Udall team. Each member of the team brings unique knowledge and skill sets to the mission, and together we are greater than the sum of the parts. The work proposed builds upon highly successful and productive cores that have been working together for over a decade. The clinical, genetic and pathologic resources are rivaled by few centers. The Mayo Udall Center is a unique complement to the Udall Center program. Success of our Udall Center has been based upon building successful collaborations and generous sharing of resources and data. This proposal has the overarching goal to better understand Lewy-related PD, which is the most common form of PD. Lewy bodies are also the hallmark of DLB and PD with dementia (PDD). How PDD and DLB relate to each other is unknown, but this non-motor complication of PD is of increasing interest to the Parkinson community. Strengths of our Udall Center are the large collection of multi-incident PD families, a proven track record of success in discovery of PD genes and a large collection of PD, PDD and DLB brains in a well annotated brain bank. The research proposal has three projects and five cores: Project 1. "Identification of genetic risk factors that predict disease onset, susceptibility and progression of PD," (PL: Matthew J. Farrer, PhD);Project 2. "Identification of candidate therapeutics for a-synuclein aggregation and cytotoxicity," (PL: Shu-Hui C. Yen, PhD);Project 3. "Molecular pathology of Lewy-related cognitive dysfunction," (PL: Dennis W. Dickson, MD);Core A. Administrative (CL: Dennis W. Dickson, MD);Core B. Clinical (CL: Zbigniew K. Wszolek, MD);Core C. Genetic (CL: Matthew J. Farrer PhD);Core D. Neuropathology (CL: Dennis W. Dickson MD) and Core E. Education and Outreach (CL: Ryan J. Uitti, MD).